1. Field of the Invention
This invention relates to a process of gasifying solid fuels with gasifying agents that contain oxygen, water vapor and/or carbon dioxide, wherein coarse-grained solid fuels in particle sizes of at least 2 mm are gasified under a pressure of 5 to 150 bars in a fixed bed while said bed is slightly descending, the gasifying agents are introduced into the fixed bed from below and the incombustible mineral constituents are withdrawn from the lower end of the fixed bed as solid ash or liquid slag, and wherein fine-grained solid fuels are gasified in a fluidized bed under a pressure of 1 to 100 bars.
2. Discussion of Prior Art
The gasification of granular coal in a fixed bed is known and has been disclosed, e.g., in Ullmanns Encyklopadie der technischen Chemie, 4th edition (1977) volume 14, on pages 383 to 396. Details of the gasifying process in which the ash remains solid are apparent from U.S. Pat. Nos. 3,540,867 and 3,854,895 and the German Offenlegungsschrift No. 22 01 278. The modification of the process involving a withdrawal of liquid slag is explained in British Nos. 1,507,505; 1,508,671 and 1,512,677.
The gasification of fine-grained solid fuels in a fluidized bed is known from German Offenlegungsschrift No. 26 11 191 and the corresponding U.S. Pat. No. 4,026,679 and from U.S. Pat. No. 2,662,816 and 4,077,778. The gasification of coal in a circulating fluidized bed is explained in detail in U.S. Pat. No. 4,032,305.
It is an object of the invention to provide a favorable combination of the gasification in a fixed bed and the gasification in a fluidized bed so that the solid fuels, particularly coals, which become available in a very wide particle size range as they are mined, can be gasified completely and without an agglomeration of the fine-grained solids.